| reverse transcriptons | An enzyme that converts RNA to DNA. Some viruses have only RNA as their primary genetic material. By converting their RNA genes to DNA with this enzyme, the host cell is 'tricked' into creating new copies of the virus. Useful in genetic engineering to make DNA from mRNA. (14 Nov 1997) |
|---|---|
| reverse Trendelenburg position | Supine position without flexing or extending, in which the head is higher than the feet. (05 Mar 2000) |
| HIV-1 reverse transcriptase | <enzyme> HIV-1 enzyme responsible for the synthesis of DNA from genomic RNA of the virus. It is encoded by the pol gene of HIV-1. Registry number: EC 2.7.7.- (12 Dec 1998) |
| HIV-2 reverse transcriptase | <enzyme> Responsible for synthesis of double-stranded DNA from the genomic RNA of the virus; has rnase h and DNA-dependent DNA polymerase activities; was indexed as reverse transcriptase (87-91) Registry number: EC 2.7.7.- (26 Jun 1999) |
| DNA reverse gyrase | <enzyme> A topoisomerase II subclass which introduces positive superhelical turns into DNA Registry number: EC 3.1.- Synonym: reverse gyrase (26 Jun 1999) |
| triiodothyronine, reverse | <chemical> 0-(4-hydroxy-3,5-diiodophenyl)-3-iodo-l-tyrosine. A metabolite of thyroxine formed by the peripheral degradation of thyroxine as a result of the tyrosyl or inner ring 5-deiodination. In systemic disease states or in neonates, levels of triiodothyronine are low and those of reverse triiodothyronine are elevated. Reverse t3 is therefore useful as a diagnostic aid and in the treatment of foetal and infantile hypothyroidism. Chemical name: L-Tyrosine, O-(4-hydroxy-3,5-diiodophenyl)-3-iodo- (12 Dec 1998) |
| acquired mutation | A change in a gene or chromosome that occurs in a single cell after the conception of the individual. That change is then passed along to all cells descended from that cell. Acquired mutations are involved in the development of cancer. (12 Dec 1998) |
| addition-deletion mutation | <molecular biology> A type of mutation that results from insertion or deletion of a single nucleotide into, or from, an open reading frame in the normal DNA sequence. Normally, the genetic code is read in the wrong frame, three nucleotides at a time, and the entire sequence downstream of the mutation, is translated into a polypeptide with a garbled amino acid sequence from the mutated codon onwards. These mutations may be induced by certain types of mutagens or may occur spontaneously and usually result in the generation, downstream, of nonsense, chain termination codons. Synonym: addition mutation, addition-deletion mutation, deletion mutation, reading-frameshift mutation. (21 Jun 2000) |
| addition mutation | <molecular biology> A type of mutation that results from insertion or deletion of a single nucleotide into, or from, an open reading frame in the normal DNA sequence. Normally, the genetic code is read in the wrong frame, three nucleotides at a time, and the entire sequence downstream of the mutation, is translated into a polypeptide with a garbled amino acid sequence from the mutated codon onwards. These mutations may be induced by certain types of mutagens or may occur spontaneously and usually result in the generation, downstream, of nonsense, chain termination codons. Synonym: addition mutation, addition-deletion mutation, deletion mutation, reading-frameshift mutation. (21 Jun 2000) |
| amber mutation | <molecular biology> A mutation from a codon which codes for an amino acid into the amber codon UAG, which normally signals that the translation of mRNA into an amino acid chain should stop. The mutation causes the amino acid chain to stop forming before it is actually completed. (09 Oct 1997) |
| back mutation | <molecular biology> A mutation that causes a mutant gene to revert to its original wild-type base sequence. Compare: forward mutation. (09 Oct 1997) |
| reading-frameshift mutation | <molecular biology> A type of mutation that results from insertion or deletion of a single nucleotide into, or from, an open reading frame in the normal DNA sequence. Normally, the genetic code is read in the wrong frame, three nucleotides at a time, and the entire sequence downstream of the mutation, is translated into a polypeptide with a garbled amino acid sequence from the mutated codon onwards. These mutations may be induced by certain types of mutagens or may occur spontaneously and usually result in the generation, downstream, of nonsense, chain termination codons. Synonym: addition mutation, addition-deletion mutation, deletion mutation, reading-frameshift mutation. (21 Jun 2000) |
| germinal mutation | A mutation in the germ cells (the cells which will undergo meiosis to form the gametes). Such mutations are therefore passed on to offspring. (09 Oct 1997) |
| germ-line mutation | Any detectable and heritable alteration in the lineage of germ cells. Mutations in these cells (i.e., "generative" cells ancestral to the gametes) are transmitted to progeny while those in somatic cells are not. (12 Dec 1998) |
| chromosomal mutation | Can refer to any of a number of DNA mutations which results in a change in the protein encoded by the mutated gene, such as point mutations, insertion or deletion mutations (frameshift mutations), or nonsense mutations. More often this refers to mutations involving chromosomes, such as the inversion of part of one chromosome such that the inverted part no longer matches with its homologous pair, a translocation of one part of a chromosome to a different chromosome, deletions of parts of chromosomes, or accidents which happen during the division of the nucleus like the unequal portioning of chromosomes between the daughter cells. (09 Oct 1997) |